The present invention relates to an in-vehicle motor-driven compressor and a controller configured to control an inverter that drives an in-vehicle three-phase motor.
A known inverter drives, for example, an in-vehicle three-phase motor included in an in-vehicle motor-driven compressor (e.g, refer to Japanese Laid-Open Patent Publication No. 2007-318824). When activating such an in-vehicle three-phase motor, the magnetic pole position of the rotor, when the rotor is stopped, may need to be obtained.
In one example of a configuration for obtaining the magnetic pole position of the stopped rotor, a position sensor may be set in the motor. However, the use of the position sensor increases the number of components. Additionally, the location where the in-vehicle three-phase motor is installed may impose limitations on the arrangement of the position sensor. In this regard, for example, as described in Japanese Patent No. 4680280, the magnetic saturation of the coils in the in-vehicle three-phase motor may be used to estimate a range that includes the magnetic pole position of the stopped rotor.
To accurately control the in-vehicle three-phase motor, instead of the magnetic pole position range of the stopped rotor, a specific numerical value (angle) of the magnetic pole position of the stopped rotor may need to be obtained. Thus, there is room for improvement in a configuration for obtaining the magnetic pole position of the stopped rotor.
It is an object of the present invention to provide a controller that controls an inverter for driving an in-vehicle three-phase motor and accurately obtains the magnetic pole position of a stopped rotor and an in-vehicle motor-driven compressor that includes the controller.
To achieve the above object, a first aspect of the invention provides a controller configured to control an inverter that drives an in-vehicle three-phase motor. The in-vehicle three-phase motor includes a u-phase coil, a v-phase coil, a w-phase coil, and a rotor incorporating a permanent magnet. The controller includes a voltage application unit, a current obtaining unit, an addition unit, an addition conversion unit, and a derivation unit. The voltage application unit is configured to apply a voltage having a predetermined pulse width to each of the phase coils in a positive direction and a negative direction. The current obtaining unit is configured to obtain a u-phase current in the positive direction, a u-phase current in the negative direction, a v-phase current in the positive direction, a v-phase current in the negative direction, a w-phase current in the positive direction, and a w-phase current in the negative direction that flow when the voltage application unit applies a voltage. The addition unit is configured to calculate a u-phase addition value by adding the u-phase current in the positive direction and the u-phase current in the negative direction, a v-phase addition value by adding the v-phase current in the positive direction and the v-phase current in the negative direction, and a w-phase addition value by adding the w-phase current in the positive direction and the w-phase current in the negative direction. The addition conversion unit is configured to perform a three-phase to two-phase conversion on the three addition values, which are the calculation results of the addition unit. The derivation unit is configured to derive a magnetic pole position of the rotor, when the rotor is stopped, based on the conversion result of the addition conversion unit.
To achieve the above object, a second aspect of the invention provides an in-vehicle three-phase compressor that includes an in-vehicle three-phase motor having a u-phase coil, a v-phase coil, a w-phase coil, and a rotor incorporating a permanent magnet, a compression portion that is driven by the in-vehicle three-phase motor and compresses a fluid, an inverter that drives the in-vehicle three-phase motor, and the controller of the first aspect.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.